Background: Spontaneous rupture of a hepatic hydatid cyst resulting in biliary peritonitis is an infrequent but severe complication that requires urgent surgical intervention and has high rates of morbidity and mortality. There are very few reported cases of this complication in the medical literature.
 Case Presentation: We present an unusual case of a 64-year-old male who presented with acute peritonitis due to biliary peritonitis resulting from the spontaneous rupture of a large hydatid cyst of the liver, as seen on contrast-enhanced computed tomography, which also showed intraperitoneal fluid. During the operation, approximately 4L of infected bile was found in the peritoneal cavity, and a cystobiliary communication was observed with rupture of the anterior wall of the cyst. Treatment involved unroofing the cyst and closing the communication. The patient was free of recurrence and in good health after 6 months of follow-up.
 Conclusion: Although this complication is rare, it should be considered in the differential diagnosis of acute abdominal pain in patients living in endemic areas.